The present invention relates to refrigerant compositions suitable for ultralow temperature refrigerating machines using non-azeotrope refrigerants, and secure from breaking the ozonosphere.
Conventionally, in a refrigerating machine using non-azeotrope refrigerants, the lower boiling point refrigerants are condensed in order by evaporating the higher boiling point refrigerants and using the low-temperature fed-back refrigerant. from the final stage evaporator, and thereby the lowest boiling point refrigerant is evaporated at the final stage to obtain an ultralow temperature.
The inventor of the present case has proposed such a refrigerating machine and an example of refrigerant composition in Japanese Patent Publication No. 6-55944. 
However, because HCFC is used as this refrigerant, there is a fear of breaking the ozonosphere of the earth.
Therefore, the development of a substitutable refrigerant composition that is secure from breaking the ozonosphere and enables a conventional refrigerating circuit to maintain its performance without changing the circuit configuration has been demanded.
An object of the present invention is to provide such a refrigerant composition and a refrigerating circuit using it. Generally in the field of refrigerant, types of refrigerants are defined by refrigerant numbers according to ASHRAE, so the description is made generally using such refrigerant numbers.
A refrigerant composition of the present invention is characterized by comprising R600 (n-butane: CH3CH2CH2CH3), R125 (pentafluoroethane: CHF2CF3), R23 (trifluoromethane: CHF3), and R14 (tetrafluoromethane: CF4).
Besides, a refrigerant composition of the present invention is characterized by comprising R600 (n-butane: CH3CH2CH2CH3), R125 (pentafluoroethane: CHF2CF3), R508A (R23/R116: 39/61), and R14 (tetrafluoromethane: CF4). Besides, the refrigerant composition of the present invention is characterized in that R600 is 28.6 to 42.9 wt. %, R125 is 10.7 to 28.6 wt. %, R508A is 14.3 to 28.6 wt. %, and R14 is 19.6 to 46.4 wt. %.
Besides, a refrigerant composition of the present invention is characterized by comprising R600 (n-butane: CH3CH2CH2CH3), R125 (pentafluoroethane: CHF2CF3), R508B (R23/R116: 46/54), and R14 (tetrafluoromethane: CF4).
Besides, the refrigerant composition of the present invention is characterized in that R600 is 28.6 to 42.9 wt. %, R125 is 10.7 to 28.6 wt. %, R508B is 14.3 to 28.6 wt. %, and R14 is 19.6 to 46.4 wt. %.
Besides, the present invention is characterized in that any of the above-described non-azeotrope refrigerant compositions is used in a refrigerating circuit as a one-way ultralow-temperature system substantially comprising one set of a condenser, an evaporator, and a compressor, and heat exchangers and gas/liquid separators disposed in multistage.
Besides, the present invention is a refrigerating circuit characterized in that any of the above-described refrigerant compositions is used without any change in a refrigerating circuit which is a one-way ultralow-temperature refrigerating circuit using a conventional CFC mixture refrigerant or HCFC mixture refrigerant and in which alkyl benzene oil (viscosity grade VG22 to VG56) is used as refrigerating machine oil.
The refrigerant compositions of the present application are non-azeotrope refrigerant compositions capable of retrofoot.